FIG. 1 is a diagram of a frame structure of a Frequency Division Duplex (FDD) mode of a Long Term Evolution (LTE) system, and as shown in FIG. 1, in the frame structure of the FDD mode, one 10 ms-radio frame is comprised of 20 slots with a length of 0.5 ms and numbered from 0 to 19, and slots 2i and 2i+1 constitute a subframe i with a length of 1 ms. FIG. 2 is a diagram of a frame structure of a Time Division Duplex (TDD) mode of an LTE system, and as shown in FIG. 2, in the frame structure of the TDD mode, one 10 ms radio frame is comprised of 2 half frames with a length of 5 ms, each of which includes 5 subframes with a length of 1 ms. Subframe i is defined as 2 slots 2i and 2i+1 with a length of 0.5 ms. In the two frame structures, for a normal Cyclic Prefix (normal CP), one slot includes 7 symbols with a length of 66.7 us, wherein, a CP length of the first symbol is 5.12 us, and a CP length of each of the remaining 6 symbols is 4.69 us; and for an extended Cyclic Prefix, one slot includes 6 symbols, and a CP length of each of all symbols is 16.67 us.
In a release (R for short) 8/9 of the LTE system and R10 of an LTE-Advanced system, a Physical Downlink Control Channel (PDCCH for short) for transmitting physical layer control signaling is generally configured to be transmitted on first N Orthogonal Frequency Division Multiplexing (OFDM) symbols of a subframe, and the N symbols are generally be referred to as a control signaling transmission region. Here, in order to be distinguished from a control signaling transmission region newly added in the new release, the control signaling transmission region of the R8/9/10 is referred to as a first control signaling transmission region in the embodiments of the present document.
Available transmission resources of the first control signaling transmission region are divided into multiple Control Channel Element (CCE) resource units, and resources occupied by the control information are allocated with the CCE being a unit. The resource unit CCE here can further be subdivided into multiple Resource Element Groups (REGs), and one CCE is comprised by multiple non-localized REGs. Generally, 9 REGs constitute one CCE, and each REG is comprised of multiple basic resource units of Resource Elements (REs).
It can be seen that the control signaling transmission resources allocated by a user are not localized, and bring out many difficulties to the implementation of the closed-loop precoding technology in a multi-antenna system, and therefore, only the diversity technology can be used in the control signaling region, and it is difficult to use the closed-loop precoding technology. The primary reason is that it is difficult to design the demodulation reference signal and channel state information feedback in the first precoding region, and therefore, the control signaling in all the existing releases only support non-localized resource transmission and diversity technologies.
In releases after R10, in order to enhance the transmission capacity of the control channel and support control signaling of more users, it is considered to develop new control channel region in the design, and control signaling transmission resources of the same User Equipment (UE) may be localized time-frequency resources, to support the closed-loop precoding technology, and enhance the transmission performance of the control information. The control signaling regions of the new and old releases are as shown in FIG. 3.
For the control signaling of the new release, a part of transmission resources are set aside from the Physical Downlink Shared Channel (PDSCH) transmission region of the original R8/9/10 to be used as the second control signaling transmission region, which enables to support the closed-loop precoding technology while transmitting the control signaling, and enhances the capacity of the control signaling to support control signaling of more users. Here, the second control signaling transmission region can reuse a Demodulation Reference Signal (DMRS) in R10 to demodulate the control signaling, which well supports the precoding technology. In addition, the second control signaling transmission region is in units of Resource Blocks (RBs), which can well perform interference coordination. Meanwhile, in consideration of robustness of the transmission and the condition that there is no channel information, in the second control signaling transmission region, the DMRS can also support the open-loop diversity technology, for example, a Space-Frequency Block Coding (SFBC) technology.
In order to better understand the background of the technical scheme of the present document, the definition of the resources of the LTE-A will be simply introduced blow. In the LTE, one RE is one subcarrier on one OFDM symbol, while one downlink physical RB is comprised of 12 localized subcarriers and 14 (12 when an extended CP is used) localized OFDM symbols, and the RB is 180 kHz in the frequency domain and is generally a time length of one slot in the time domain, as shown in FIG. 4 (one 5M system). When allocating resources, the LTE/LTE-A system allocates the resources with RB being a basic unit.
For the PDSCH dynamically scheduled in an LTE FDD mode, resource indexes for transmitting a Physical Uplink Control Channel (PUCCH) carrying a Hybrid Automatic Repeat Request Acknowledgment (HARQ-ACK) in an uplink are implicitly mapped by a minimum CCE index corresponding to a PDCCH allocated to the user on scheduled downlink subframes. That is, nPUCCH(1)=nCCE+NPUCCH(1), wherein, nPUCCH(1) is a PUCCH resource index for transmitting a HARQ-ACK by a user, nCCE is a first CCE index for transmitting the PDCCH, and NPUCCH(1) is configured by a higher layer. For the PDSCH transmission indicated by the PDCCH or the transmission released by the downlink Semi-Persistent Scheduling (SPS) indicated by the PDCCH in the LTE TDD mode, resource indexes for transmitting the PUCCH carrying the HARQ-ACK in the uplink are obtained after block interleaving the CCE indexes corresponding to the PDCCH allocated to the user on the scheduled downlink subframes. As there will be a configuration in the TDD mode that the number of downlink subframes is greater than the number of uplink subframes in one radio frame, a concept of feedback window is defined. The feedback window is all downlink subframes corresponding to uplink subframes (it should be illustrated that “corresponding” here refers to all these downlink subframes feed back confirmation information in the uplink subframes).
For the TDD mode, as there may be a scenario that the number of downlink subframes is greater than the number of uplink subframes in one radio frame, feedback information of multiple downlink subframes may be transmitted in the same uplink subframe. Such multiple downlink subframes corresponding to one uplink subframe are referred to as a feedback window.
For PDSCH transmission not indicated by the PDCCH, nPUCCH(1) is configured by a higher layer and is decided by table one. Table one illustrates a relationship between PUCCH resource indexes and signaling.
TABLE ONERelationship between PUCCH resource indexes and signalingTransmit Power Control(TPC) domain valuenPUCCH(1)‘00’First PUCCH resource index configured by ahigher layer‘01’Second PUCCH resource index configured bya higher layer‘10’Third PUCCH resource index configured by ahigher layer‘11’Fourth PUCCH resource index configured bya higher layer
For downlink SPS PDSCH indicated by Downlink Control Information (DCI for short) signaling, nPUCCH(1) of the PDSCH is determined by one of four resources configured by a higher layer indicated by a TPC domain.
At present, in a process of constant development of the LTE-Advanced, the system capacity is expanded to support increasing requirements on the number of users, and the existing PDCCH can not satisfy requirements on more advanced wireless communication systems. To this end, in the discussion of the 3rd Generation Partnership Project (3GPP), an Enhanced PDCCH (ePDCCH) is introduced to enhance the performance of the PDCCH, and at the same time, a new PDCCH transmission region is introduced, and an Enhanced Control Channel Element (eCCE) for carrying an ePDCCH is defined. At this time, how to obtain PUCCH resources for transmitting ACK/NACK corresponding to the PDSCH of the ePDCCH is a problem to be solved.